OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To modify the shadow mapping algorithm and to use this random sampling technique, perform the following steps. We'll build the offset texture within the main OpenGL program, and make use of it within the fragment shader:

1. Use the following code within the main OpenGL program to create the offset texture. This only needs to be executed once during the program's initialization:

void buildOffsetTex(int size, int samplesU, int samplesV) { int samples = samplesU * samplesV; int bufSize = size * size * samples * 2; float *data = new float[bufSize]; for( int i = 0; i< size; i++ ) { for(int j = 0; j < size; j++ ) { for( int k = 0; k < samples; k += 2 ) { int x1,y1,x2,y2; x1 = k % (samplesU); y1 = (samples - 1 - k) / samplesU; x2 ...